The skeletal system includes many long bones that extend from the human torso. These long bones include the femur, fibula, tibia, humerus, radius and ulna. These long bones are particularly exposed to trauma from accidents, and, as such, may be easily fractured.
When a fracture occurs, the distal end or proximal portions of the long bone may be fractured into several components and must be realigned. For example, subtrochanteric and femoral shaft fractures of femurs are often accompanied by fractures of the femoral neck portion and head portion. Areas around the greater trochanter and lesser trochanter may also fracture.
Mechanical devices, commonly in the forms of pins, plates, screws, nails, wires and external devices are commonly used to attach fractured long bones. The pins, plates, wires, nails and screws are typically made of a durable material compatible to the human body, for example titanium, stainless steel or cobalt chromium.
One mechanical device commonly used to treat subtrochanteric and femoral shaft fractures is the intramedullary rod or nail. The intramedullary nail is typically provided as a cannulated shaft that is inserted into the marrow canal of the femur or other long bone in order to stabilize the fractured bone parts. Before the intramedullary nail is inserted into a long bone, a ball-nose guide wire is typically inserted into the bone canal. The intramedullary nail follows the guide wire into the canal. The guide wire is then removed from the canal and further work may be done on the bone with the implanted intramedullary nail.
Intramedullary rods or nails are often provided with openings for receiving transverse screws or pins. These transverse screws are used to secure the femoral bone fragments, for example the greater trochanter, the lesser trochanter, the neck portion, and the head portion. When securing bone fragments of the neck portion and head portion of the femur, a transverse screw in the form of a lag screw is typically fitted through an opening in the intramedullary nail and screwed into the neck portion and head portion of the fractured femur. At the option of the surgeon, an anti-rotation peg or screw may also be positioned in a second opening in the intramedullary nail to provide a more rigid construction for securing the fractured bone fragments of the femoral neck and head.
To promote the healing of the bone fracture the lag screw and anti-rotation screw are designed to provide a load or force on the reduction or fracture site. Accordingly, the lag screw and anti-rotation screw are designed to provide for sliding compression or movement of the screws in the openings of the intramedullary nail when the intramedullary nail is implanted in the patient during surgery. However, following implantation, during the healing process, movement of the screws relative to the bone is undesirable.
In order to reduce movement of the screws following surgery, some locking device is typically inserted into the intramedullary nail to engage the screws and limit their motion relative to the nail. However, before the locking piece may be inserted into the nail, the ball-nose guide wire must first be removed from the nail. Thus, the locking device is not typically preinstalled in the intramedullary nail and instead must be inserted during the surgical procedure. This process of installing the locking device takes up valuable time during the surgery and is generally inconvenient for the surgeon. Accordingly, it would be advantageous to provide an intramedullary nail arrangement having a locking piece that is pre-installed in the nail before the surgical procedure.
During a surgical procedure where the surgeon uses both a lag screw and an anti-rotation screw, a surgeon may wish to independently lock down the lag screw or the anti-rotational screw to control the rotational and axial translation of one screw while allowing the other screw to move independently. However, current intramedullary nail arrangements do not provide the option to lock down the lag screw while allowing the anti-rotation screw to move independently. Accordingly, it would also be advantageous to provide an intramedullary nail arrangement where the lag screw may be locked down while still allowing the anti-rotation screw to move independently.
Some prior art arrangements have utilized a set screw and spacer provided in the intramedullary nail to control the lag screw. However, in these arrangements, the set screw and spacer are two separate pieces. This is also not optimal because the complete assembly is not cannulated and does not allow the lag screw to translate along its axis. Furthermore, other proposed arrangements for controlling movement of the lag screw do not allow for an anti-rotation screw when desired. For these intramedullary nails having a lag screw but no option for an anti-rotation screw, some means may be provided to screw down a pin or rod to either statically lock the lag screw or only allow translation. However, in past arrangements calling for both a lag screw and an anti-rotation screw no means is provided for controlling only the lag screw with the anti-rotation screw in place or for locking the lag screw while still allowing translation of the anti-rotation screw.
Therefore, it would be advantageous to provide an improved intramedullary nail assembly. As discussed above, it would be particularly advantageous to provide an intramedullary nail assembly where a locking piece may be preinstalled in the nail prior to surgery. It would also be advantageous if such intramedullary nail assembly was configured to include both a lag screw and an optional anti-rotation screw that may be selectively locked in place on the nail assembly. Furthermore, it would be advantageous if the intramedullary nail assembly included an arrangement to control movement of the lag screw with the anti-rotation screw in place in the intramedullary nail or for locking only the lag screw while still allowing translation of the anti-rotation screw within the intramedullary nail.